I'd say that's, at the very least, an oversimplification; when you look at the architecture of organizations generally recognized as cults, you end up finding they share a fairly specific cluster of cultural characteristics, one that has more to do with internal organization than claims of certainty. My favorite framework for this is the amusingly named ABCDEF: though aimed at new religions in the neopagan space, it's general enough to be applied outside it.

(Eliezer, of course, would say that every cause wants to be a cult. I think he's being too free with the word, myself.)